Embodiments of the disclosure relate to a rollable glass sheet configured to reversibly transition between a flat configuration and a bent configuration. The rollable glass sheet includes a first major surface and a second major surface opposite to the first major surface. The first major surface and the second major surface define a thickness of the glass sheet that is 0.4 mm or less. In the flat configuration, the first major surface includes a first surface compressive stress and a first depth of compression, and in the bent configuration, the first major surface includes a curvature. At a radius of curvature of 50 mm, the first major surface includes a second surface compressive stress less than the first compressive stress and a second depth of compression less than the first depth of compression and greater than 11 μm.
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1. A rollable glass sheet configured to reversibly transition between a flat configuration and a bent configuration, the rollable glass sheet comprising:
a first major surface;
a second major surface opposite to the first major surface, the first major surface and the second major surface defining a thickness of the glass sheet, wherein the thickness is from 0.21 mm to 0.4 mm;
wherein, in the flat configuration, the first major surface comprises a first surface compressive stress and a first depth of compression;
#11# wherein, in the bent configuration, the first major surface comprises a curvature and wherein, if the first major surface comprises radius of curvature of 50 mm, the first major surface comprises a second surface compressive stress less than the first compressive stress and a second depth of compression less than the first depth of compression and greater than 11 μm,wherein, when the thickness is 0.21 mm, the first compressive stress is from 530 mpa to 945 mpa and the first depth of compression is from 32 μm to 36 μm, wherein a maximum, and
wherein, when the thickness is 0.40 mm, the first compressive stress is from 730 mpa to 1000 mpa and the first depth of compression is from 38 μm to 42 μm.
2. The rollable glass sheet of
6. The rollable glass sheet of
7. The rollable glass sheet of
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This application claims the benefit of priority under 35 U.S.C. § 119 of U.S. Provisional Application Ser. No. 63/031,617 filed on May 29, 2020, the content of which is relied upon and incorporated herein by reference in its entirety.
The disclosure relates to vehicle interior systems, in particular to a rollable or foldable glass sheet that can be used in a retractable display system of a vehicle interior system.
Vehicle interiors include a variety of displays for information and entertainment. For example, a vehicle interior may include an instrument cluster behind the steering wheel providing information on current speed, rpms, tire pressure, maintenance warnings, fuel level, coolant temperature, etc. Additionally, the center console may include an entertainment or control center with a touchscreen display for manipulating the audio system, GPS, cabin temperature, etc. Besides the additional functionality provided by these displays, efforts are made to incorporate them in the cabin interior in an unobtrusive or aesthetically pleasing way, especially by blending the display with the textures or patterns of the vehicle interior.
According to an aspect, embodiments of the disclosure relate to a rollable glass sheet configured to reversibly transition between a flat configuration and a bent configuration. The rollable glass sheet includes a first major surface and a second major surface opposite to the first major surface. The first major surface and the second major surface define a thickness of the glass sheet that is 0.4 mm or less. In the flat configuration, the first major surface includes a first surface compressive stress and a first depth of compression, and in the bent configuration, the first major surface includes a curvature. Ata radius of curvature of 50 mm, the first major surface includes a second surface compressive stress less than the first compressive stress and a second depth of compression less than the first depth of compression and greater than 11 μm.
According to another aspect, embodiments of the disclosure relate to a display system for a vehicle interior system. The display system includes a support structure and a glass sheet connected to the support structure. The glass sheet includes a first major surface and a second major surface opposite to the first major surface. The first major surface and the second major surface define a thickness of the glass sheet. The thickness is 0.4 mm or less. The glass sheet is configured to reversibly transition between a retracted configuration and a deployed configuration. The support structure reinforces the glass sheet in the deployed configuration. In the deployed configuration, the glass sheet has a planar section having a central tension between the first major surface and the second major surface. The central tension is from 95 MPa to 175 MPa. In the retracted configuration, the second major surface includes a curved region, and at a radius of curvature of 50 mm, the second major surface in the curved region has a bent depth of compression of greater than 11 μm.
According to still another aspect, embodiments of the disclosure relate to a method in which a glass sheet is retracted from a deployed configuration to a retracted configuration. The glass sheet includes a first major surface and a second major surface opposite to the first major surface. The first major surface and the second major surface define a thickness of the glass sheet. The thickness is 0.4 mm or less. In the deployed configuration, the glass sheet has a planar section having a central tension between the first major surface and the second major surface. The central tension is from 95 MPa to 175 MPa. In the retracted configuration, the second major surface includes a curved region, and at a radius of curvature of 50 mm, the second major surface in the curved region has a first depth of compression of greater than 11 μm.
Additional features and advantages will be set forth in the detailed description which follows, and in part will be readily apparent to those skilled in the art from that description or recognized by practicing the embodiments as described herein, including the detailed description which follows, the claims, as well as the appended drawings.
It is to be understood that both the foregoing general description and the following detailed description are merely exemplary, and are intended to provide an overview or framework to understanding the nature and character of the claims. The accompanying drawings are included to provide a further understanding, and are incorporated in and constitute a part of this specification.
The accompanying drawings incorporated in and forming a part of the specification illustrate several aspects of the present invention and, together with the description, serve to explain the principles of the invention. In the drawings:
Reference will now be made in detail to various embodiments, examples of which are illustrated in the accompanying drawings. In general, the various embodiments pertain to a vehicle interior system having a rollable or foldable display screen. In the embodiments discussed herein, the display screen extends from a rolled or folded (i.e., storage) configuration interior to the vehicle interior system to a flat (i.e., deployed) configuration exterior to the vehicle interior system. The glass sheet used for the display screen is configured to be bent to a radius of curvature of 50 mm (or even lower in certain applications) to wind around a reel on the interior of the vehicle interior system. In order to prevent breakage in the stored configuration, the glass sheet is ion-exchange strengthened so as to ensure that the depth of compressive stress (DOC) at a bend radius of 50 mm is greater than 11 μm, which is the average edge flaw depth for glass sheets used in vehicle interiors. Further, in order to meet relevant headform impact testing (HIT) requirements in the deployed configuration, the glass sheet is ion-exchange strengthened so as to ensure that the DOC at a bend radius of 50 mm is less than 19 μm, which is a DOC indicative of too high of a central tension in the deployed configuration to meet HIT requirements. Various embodiments of the glass sheet, display system, vehicle interior system incorporating the display system, and methods of deploying/retracting the display system are disclosed herein. These embodiments are provided by way of illustration and not by way of limitation.
In embodiments, the radius of curvature R of the retraction mechanism 22 is relatively small given that the retraction mechanism 22 is configured to be mounted in the dashboard, which may have limited space in view of all the other typical controls, vents, electronics, etc. contained in the dashboard space. Thus, in embodiments, the retraction mechanism 22 may have a radius of curvature R of, for example about 20 mm to about 100 mm. For the example embodiments discussed below, a radius curvature R of 50 mm was considered. However, in other embodiments, the radius of curvature R may be larger depending on where in the vehicle that the display system 12 is installed.
Because of the thinness of the glass sheet 16 and display 30 (when provided), a support structure 32 may be provided to keep the glass sheet 16 and display 30 upright and to provide flexural rigidity to the display system 12 in the deployed state. In embodiments, the support structure 32 is a telescoping frame 34 that extends through the opening 18 from inside the dashboard 14. In embodiments, the telescoping frame 34 is connected to the endcap 20 so that, as the retraction mechanism 22 deploys and retracts the glass sheet 16, the endcap 20 telescopes or collapses the telescoping frame 34.
In embodiments in which the glass sheet 16 rolls around the retraction mechanism 22, the retraction mechanism 22 may be a motor-driven rotatable shaft 36 to which a second end of the glass sheet 16 is fixed (e.g., by a fastener or adhesive). By driving the rotatable shaft 36, the second end of the glass sheet 16, by virtue of being fixed to the rotatable shaft 36, will cause the glass sheet 16 to roll or unroll for retraction or deployment, respectively. As shown in
While each of the embodiments shown in
In other embodiments, the support structure 32 may be a thin piece of sheet metal that rolls or folds with the glass sheet 16. In still other embodiments, the support structure 32 may be guide rails adhered to the second major surface 26 that follow tracks. The guide rails may be connected by cross members (such as cross members 46 as shown in
Independent of the retraction mechanism 22 and support structure 32, the glass sheet 16 may be configured to stop at various positions between the fully retracted and full extended states. In embodiments, the glass sheet 16 extends a height of up to 250 mm above the dashboard 14 in the fully extended state. Further, in embodiments, the glass sheet 16 has a width of up to 200 mm. These dimensions are merely illustrative. A vehicle having more room could accommodate a larger screen.
In order to meet the requirements of headform impact testing (HIT) according to FMVSS 201, the glass sheet 16 is strengthened. Specifically, to pass HIT requirements, the display device 12, upon being impacted by a headform, must not allow the headform to decelerate in a manner that the headform exceeds 80 g of force continuously for a duration of 3 ms or more.
In particular embodiments, the glass sheet 16 is chemically strengthened through an ion exchange process. Details of exemplary ion exchange processes are provided further below. The strengthened glass sheet 16 will have a surface compressive stress (CS) on the first major surface 24 and on the second major surface 26. The compressive stress is at a maximum at the first and second major surfaces 24, 26 and will gradually taper going towards the interior. The compressive stress will reach zero, and the distance from the surface to the point where compressive stress reaches zero is referred to the depth of compressive stress (DOC). Thereafter, the stress transitions to a tension stress, reaching a maximum central tension (CT) generally at or near the center of the thickness. The CS, DOC, and CT all have an effect on the performance of the glass sheet 16 in HIT. In embodiments, the flat CS of the glass sheet 16 is in the range of 550 MPa to 1000 MPa, in particular, in the range of 550 MPa to 900 MPa. Further, in embodiments, the flat CT is in the range of 95 MPa to 175 MPa. In still further embodiments, the DOC is at least 32 μm.
Further, the CS and DOC, in particular, have an effect on the bending performance of the glass sheet 16. Because of the way that the glass sheet 16 is rolled or bent, the first major surface 24 will have a different CS and DOC than the second major surface 26. Assuming equal CS and DOC on the first and second surfaces 24, 26 in a flat configuration, the CS and DOC on the first major surface 24, which is on the interior of the curve, will increase, and the CS and DOC on the second major surface 26, which is on the exterior of the curve, will decrease. It should be noted that this discussion pertains to, e.g., the embodiments shown in
Standard edge finishing of a glass sheet 16 will typically leave edge flaws having a depth of up to 11 μm. Accordingly, as disclosed herein, the DOC on the second major surface 26 is maintained above 11 μm under 50 mm bend radius. In particular embodiments, the DOC on the second major surface 26 is maintained above 11 μm under 50 mm bend radius with a safety factor of about 1.5. Thus, the DOC on the second major surface 26 is maintained at 17 μm or more under 50 mm bend radius. However, the DOC on the second major surface 26 is also maintained below 19 μm under 50 mm bend radius so as to keep the CT from rising too high, which would have a negative impact on HIT performance. Further, in embodiments, advanced edge finishing using an HF etching can reduce edge flaws down to 3 μm or lower. Thus, in embodiments in which the glass sheet 16 undergoes advanced edge finishing, the DOC under 50 mm bend radius can be decreased even further even including a safety factor. In embodiments, the DOC under 50 mm bend radius for an advanced edge finish glass is at least 5 μm, at least 7 μm, or at least 10 μm.
The DOC under 50 mm bend radius (hereinafter referred to as “R50 DOC”) is influenced by the flat DOC and CS. In particular, when bent to a radius of 50 mm, the DOC will decrease from the flat DOC to the R50 DOC. For a relatively higher flat CS, the flat DOC can be shallower while still providing an R50 DOC within the range of 11 μm to 19 μm, in particular within the range of 17 μm to less than 19 μm. Conversely, for a relatively lower flat CS, the flat DOC will need to be deeper to provide an R50 DOC within the specified range. The following Tables 1-5 and
In particular, the following Tables 1-5 consider the flat DOC, flat CS, and R50 DOC for five thicknesses ranging from 0.21 mm to 0.40 mm. CS can be measured using those means known in the art, such as by surface stress meter (FSM) using commercially available instruments such as the FSM-6000, manufactured by Orihara Industrial Co., Ltd. (Japan). Surface stress measurements rely upon the accurate measurement of the stress optical coefficient (SOC), which is related to the birefringence of the glass. SOC in turn is measured by those methods that are known in the art, such as fiber and four point bend methods, both of which are described in ASTM standard C770-98 (2013), entitled “Standard Test Method for Measurement of Glass Stress-Optical Coefficient,” the contents of which are incorporated herein by reference in their entirety, and a bulk cylinder method.
DOC may be measured by FSM or by a scattered light polariscope (SCALP) (such as the SCALP-04 scattered light polariscope available from Glasstress Ltd., located in Tallinn Estonia), depending on the strengthening method and conditions. When the glass sheet is chemically strengthened by an ion exchange treatment, FSM or SCALP may be used depending on which ion is exchanged into the glass sheet. Where the stress in the glass sheet is generated by exchanging potassium ions into the glass sheet, FSM is used to measure DOC. Where the stress is generated by exchanging sodium ions into the glass sheet, SCALP is used to measure DOC. Where the stress in the glass sheet is generated by exchanging both potassium and sodium ions into the glass, the DOC is measured by SCALP, since it is believed the exchange depth of sodium indicates the DOC and the exchange depth of potassium ions indicates a change in the magnitude of the compressive stress (but not the change in stress from compressive to tensile); the exchange depth of potassium ions in such glass sheets is measured by FSM. CT is the maximum tensile stress and is measured by SCALP.
Knowing the CS and DOC, the CT and bending stress can be estimated using numerical models. In particular, the CT is estimated according to Equation 1, below:
in which CT is the central tension, CS is the surface compressive stress, DOC is the depth of compressive stress, and T is the thickness of the glass sheet 16.
The bend induced stress is determined by Equation 2, below:
in which σbend is the bend induced stress, E is the Young's Modulus, the v is Poisson's Ratio, T is the thickness of the glass sheet 16, x is the depth into the thickness, and R is the bend radius. The bend stress is maximum at the surface, where x=0, and the neutral axis is at the mid-thickness, or x=T/2.
The resulting shift in the stress profile resulting from bending is the superposition of the stress profile in the flat state and the linear bend stress provided Equation 2. The DOC in the bent state is determined by the zero-stress depth. The particular DOC of interest is for the second major surface 26, which will have an R50 DOC reduced from the flat DOC.
Table 1, below, considers a glass sheet 16 having a thickness T of 0.21 mm. The flat DOC is given on the right side of the table, the flat CS (in MPa) for each flat CS are provided on the interior of the table, and the resulting R50 DOC is provided across the top of the table.
TABLE 1
Flat DOC and CS (MPa) to achieve desired R50 DOC for 0.21 mm thick
glass sheet
R50 DOC
17.0 μm
18.0 μm
19.0 μm
Flat DOC
32 μm
675
775
945
33 μm
625
725
865
34 μm
590
680
805
35 μm
560
640
740
36 μm
530
600
695
As can be seen from Table 1, a flat CS of 675 MPa and a flat DOC of 32 μm will allow an R50 DOC of 17.0 μm.
Table 2, below, considers a glass sheet 16 having a thickness T of 0.25 mm. The data for flat DOC, flat CS (MPa), and R50 DOC are arranged in the same manner as Table 1.
TABLE 2
Flat DOC and CS (MPa) to achieve desired R50 DOC for 0.25 mm thick
glass sheet
R50 DOC
17.0 μm
18.0 μm
19.0 μm
Flat DOC
33 μm
720
800
940
34 μm
670
765
870
35 μm
640
720
815
36 μm
610
690
765
37 μm
590
655
725
Table 3, below, considers a glass sheet 16 having a thickness T of 0.30 mm. The data for flat DOC, flat CS (MPa), and R50 DOC are arranged in the same manner as Tables 1-2.
TABLE 3
Flat DOC and CS (MPa) to achieve desired R50 DOC for 0.30 mm thick
glass sheet
R50 DOC
17.0 μm
18.0 μm
19.0 μm
Flat DOC
35 μm
735
820
925
36 μm
700
775
875
37 μm
675
750
830
38 μm
650
715
790
39 μm
620
680
760
Table 4, below, considers a glass sheet 16 having a thickness T of 0.36 mm. The data for flat DOC, flat CS (MPa), and R50 DOC are arranged in the same manner as Tables 1-3.
TABLE 4
Flat DOC and CS (MPa) to achieve desired R50 DOC for 0.36 mm thick
glass sheet
R50 Bent DOC
17.0 μm
18.0 μm
19.0 μm
Flat DOC
37 μm
795
865
960
38 μm
760
830
915
39 μm
735
795
875
40 μm
710
765
840
41 μm
690
740
805
Table 5, below, considers a glass sheet 16 having a thickness T of 0.40 mm. The data for flat DOC, flat CS (MPa), and R50 DOC are arranged in the same manner as Tables 1-4.
TABLE 5
Flat DOC and CS (MPa) to achieve desired R50 DOC for 0.40 mm thick
glass sheet
R50 Bent DOC
17.0 μm
18.0 μm
19.0 μm
Flat DOC
38 μm
840
900
1000
39 μm
800
870
955
40 μm
775
840
920
41 μm
750
815
885
42 μm
730
786
855
With respect to the data provided in Tables 1-5 and shown in
The foregoing analysis is further supported by experimental data as will be discussed below. In the experiments, glass sheets 16 having a thickness of 0.3 mm and 0.4 mm were cut into coupons having dimensions of 200 mm×340 mm. The glass sheets 16 had a Young's modulus (E) of 71.5 GPa and a Poisson's ratio (ν) of 0.21. The glass sheets 16 were edge finished to a standard PRC bullnose using 400 and 800 grit wheels. The coupons cut from the glass sheets 16 were ion-exchanged. For the 0.3 mm thick coupons, the flat CS was 781 MPa, and the flat DOC was 36 μm. For the 0.4 mm thick coupons, the flat CS was 803 MPa, and the flat DOC was 40 μm.
Coupons were tested in 2 point bend tests to generate Weibull plots as shown in
In order to determine how the glasses of these thicknesses would respond to being rolled or folded at a particular radius of curvature for a given period of time, the allowable lifetime stress, SAL, for the 0.4 mm and 0.3 mm thick glasses was determined according to Equation 3:
SAL=S0(Fp*FS*FF)
S0 is the Weibull characteristic strength value (referenced above), FP is the probability factor, FS is the size factor, and FF is the fatigue factor. The fatigue factor FF can be ignored in this instance because the edge flaws are maintained within the DOC as discussed above. The probability factor FP is given by Equation 4:
in which R′ is the reliability and m is the Weibull modulus for the 0.3 mm thick glass coupons and 0.4 mm thick glass coupons. The reliability R′ is the desired level of parts designed to operate without failure under a given set of conditions. In this instance, the failure probability is desired to be at most 0.1% or 0.001, and thus, the reliability R is 99.9% or 0.999. Based on Equation 4, the desired reliability R′, and the Weibull parameters from the plot of
The size factor FS is given by Equation 5:
in which Lreference is the reference length used to generate the Weibull plot, which was 0.1 mm as mentioned above. Lproduct is the actual length of the product being analyzed. Here, the coupons were cut to a length of 340 mm on the sides that are to be bent. Further, there are two sides that are bent, so the total Lproduct is 2*340 mm, or 680 mm. Again, m is the Weibull modulus, which is 49 and 55 for the 0.4 mm and 0.3 mm thick glasses, respectively. Based on the foregoing parameters and Equation 5, the size factor FS is 0.835 for the 0.4 mm thick glass sheets 16, and the size factor FS is 0.852 for the 0.3 mm thick glass sheets 16.
From Equation 3, the allowable lifetime stress SAL can be determined using the Weibull characteristic strength S0, the probability factor FP, and the size factor FS. For the 0.4 mm thick glass, the allowable lifetime stress SAL was determined to be about 525 MPa (736.9*0.853*0.835), and the allowable lifetime stress SAL was determined to be about 518 MPa (699.0*0.869*0.852) for the 0.3 mm thick glass.
With knowledge of the allowable lifetime stress at the desired failure rate of 0.1%, the tightest radius at which the 0.4 mm and 0.3 mm glasses can be stored with a high degree of reliability can be determined. In particular, using the allowable lifetime stress SAL as the maximum bend stress in Equation 2, above, the radius to produce that stress can be determined. In particular, Equation 2 can be rearranged to solve for the radius of curvature R for the 0.4 mm and 0.3 mm thick glasses as shown below:
Thus, using the allowable lifetime stress SAL developed from the Weibull plot and the maximum stress from Equation 2, the minimum or tightest bend radius for the 0.4 mm thick glass was determined to be about 29 mm, and the minimum or tightest bend radius for the 0.3 mm thick glass was determined to be about 22 mm. It should be noted that the bend stress for a radius of curvature of 50 mm discussed above is well below the allowable lifetime stress for each of the 0.4 mm and 0.3 mm glasses (bend stresses of about 300 MPa and about 225 MPa, respectively). Thus, the glasses having a thickness of 0.4 mm and 0.3 mm could reliably be stored at curvatures below a radius of 50 mm, or the reliability of the 0.4 mm and 0.3 mm glasses in storage could be increased by storing them at curvatures greater than 29 mm and 22 mm, respectively.
In order to confirm these analytical and experimental observations, 0.4 mm and 0.3 mm thick glass coupons as described above were held in static bend at various curvatures for a week or longer to determine reliability performance.
TABLE 6
Static Bend Test at Various Bend Radiuses
Bend
Radius
0.3 mm thick glass coupons
0.4 mm thick glass coupons
50 mm
All 10 samples survived 1
All 10 samples survived 1
week hold
week hold
35 mm
All 10 samples survived
All 10 samples survived
1 week hold
1 week hold
25 mm
5 samples survived 1
8 samples failed
week hold,
immediately,
5 samples survived
2 samples failed within
12 week hold
10 minutes
As can be seen from Table 6, all of the sample survived static bending for 1 week at the radiuses of 50 mm and 35 mm, which was expected from the allowable lifetime stress and minimum bend radius calculations. Indeed, the discussion above indicated that both the 0.4 mm glass coupons and the 0.3 mm glass coupons would survive with high reliability at bend radiuses down to 29 mm and 22 mm, respectively. This was demonstrated at the static bend radius of 25 mm in which the 0.3 mm thick glass coupons survived, including 5 samples that we held at a 25 mm radius of curvature for 12 weeks. Further, as the minimum bend radius of 29 mm for the 0.4 mm thick glass coupons predicted, holding the 0.4 mm thick glass coupons at a lower bend radius of 25 mm caused 8 of the 10 samples to fail immediately, and the remaining two samples failed within 10 minutes. Thus, the experimental data confirmed the predictions based on the Weibull plot of
The various embodiments of the display system 12 for the vehicle interior 10 may be incorporated into vehicles such as trains, automobiles (e.g., cars, trucks, buses and the like), sea craft (boats, ships, submarines, and the like), and aircraft (e.g., drones, airplanes, jets, helicopters and the like).
As noted above, glass sheet 16 is strengthened, in particular by chemical strengthening, e.g., through ion-exchange strengthening. In the ion exchange process, ions at or near the surface of the glass sheet are replaced by—or exchanged with—larger ions having the same valence or oxidation state. In those embodiments in which the glass sheet comprises an alkali aluminosilicate glass, ions in the surface layer of the article and the larger ions are monovalent alkali metal cations, such as Li+, Na+, K+, Rb+, and Cs+. Alternatively, monovalent cations in the surface layer may be replaced with monovalent cations other than alkali metal cations, such as Ag+ or the like. In such embodiments, the monovalent ions (or cations) exchanged into the glass sheet generate a stress.
Ion exchange processes are typically carried out by immersing a glass sheet in a molten salt bath (or two or more molten salt baths) containing the larger ions to be exchanged with the smaller ions in the glass sheet. It should be noted that aqueous salt baths may also be utilized. In addition, the composition of the bath(s) may include more than one type of larger ions (e.g., Na+ and K+) or a single larger ion. It will be appreciated by those skilled in the art that parameters for the ion exchange process, including, but not limited to, bath composition and temperature, immersion time, the number of immersions of the glass sheet in a salt bath (or baths), use of multiple salt baths, additional steps such as annealing, washing, and the like, are generally determined by the composition of the glass sheet (including the structure of the article and any crystalline phases present) and the desired DOC and CS of the glass sheet that results from strengthening. Exemplary molten bath compositions may include nitrates, sulfates, and chlorides of the larger alkali metal ion. Typical nitrates include KNO3, NaNO3, LiNO3, NaSO4 and combinations thereof. The temperature of the molten salt bath typically is in a range from about 380° C. up to about 450° C., while immersion times range from about 15 minutes up to about 100 hours depending on glass sheet thickness, bath temperature and glass (or monovalent ion) diffusivity. However, temperatures and immersion times different from those described above may also be used.
In one or more embodiments, the glass sheets may be immersed in a molten salt bath of 100% NaNO3, 100% KNO3, or a combination of NaNO3 and KNO3 having a temperature from about 370° C. to about 480° C. In some embodiments, the glass sheet may be immersed in a molten mixed salt bath including from about 5% to about 90% KNO3 and from about 10% to about 95% NaNO3. In one or more embodiments, the glass sheet may be immersed in a second bath, after immersion in a first bath. The first and second baths may have different compositions and/or temperatures from one another. The immersion times in the first and second baths may vary. For example, immersion in the first bath may be longer than the immersion in the second bath.
In one or more embodiments, the glass sheet may be immersed in a molten, mixed salt bath including NaNO3 and KNO3 (e.g., 49%/51%, 50%/50%, 51%/49%) having a temperature less than about 420° C. (e.g., about 400° C. or about 380° C.). for less than about 5 hours, or even about 4 hours or less.
Ion exchange conditions can be tailored to provide a “spike” or to increase the slope of the stress profile at or near the surface of the resulting glass sheet. The spike may result in a greater surface CS value. This spike can be achieved by a single bath or multiple baths, with the bath(s) having a single composition or mixed composition, due to the unique properties of the glass compositions used in the glass sheets described herein.
In one or more embodiments, where more than one monovalent ion is exchanged into the glass sheet, the different monovalent ions may exchange to different depths within the glass sheet (and generate different magnitudes stresses within the glass sheet at different depths). The resulting relative depths of the stress-generating ions can be determined and cause different characteristics of the stress profile.
Suitable glass compositions for use in glass sheet 16 include soda lime glass, aluminosilicate glass, borosilicate glass, boroaluminosilicate glass, alkali-containing aluminosilicate glass, alkali-containing borosilicate glass, and alkali-containing boroaluminosilicate glass.
In one or more embodiments, the glass composition may include SiO2 in an amount in a range from about 66 mol % to about 80 mol %, Al2O3 in an amount in a range from about 4 mol % to about 15 mol %, B2O3 in an amount in a range from about 0 mol % to about 5 mol %, P2O5 in an amount in a range from about 0 mol % to about 2 mol %, R2O in an amount in a range from about 8 mol % to about 20 mol %, RO in an amount in a range of from about 0 mol % to about 2 mol %, ZrO2 in an amount in a range of from about 0 mol % to about 0.2 mol %, and SnO2 in an amount in a range from about 0 mol % to about 0.2 mol %. In the foregoing composition, R2O refers to the total amount of alkali metal oxides, such as Li2O, Na2O, K2O, Rb2O, and Cs2O). In particular, Na2O may be present in an amount in a range from about from about 8 mol % to about 20 mol %, and K2O may be present in an amount in a range from about 0 mol % to about 4 mol %. Further, in the foregoing composition, RO refers to the total amount of alkaline earth metal oxide such, as CaO, MgO, BaO, ZnO and SrO. In particular, CaO may be present in an amount in a range of from about 0 mol % to about 1 mol %, and MgO may be present in an amount in a range of from about 0 mol % to about 7 mol %.
In embodiments, the glass composition may include other oxides of such metals as Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Ce, W, and Mo. In particular, Fe in the form of Fe2O3 may be present in an amount in a range of from about 0 mol % to about 1 mol %, and TiO2 may be present in an amount of in a range of about 0 mol % to about 5 mol %.
An exemplary glass composition includes SiO2 in an amount in a range from about 65 mol % to about 75 mol %, Al2O3 in an amount in a range from about 8 mol % to about 14 mol %, Na2O in an amount in a range from about 12 mol % to about 17 mol %, K2O in an amount in a range of about 0 mol % to about 0.2 mol %, and MgO in an amount in a range from about 1.5 mol % to about 6 mol %. Optionally, SnO2 may be included in the amounts otherwise disclosed herein.
Unless otherwise expressly stated, it is in no way intended that any method set forth herein be construed as requiring that its steps be performed in a specific order. Accordingly, where a method claim does not actually recite an order to be followed by its steps or it is not otherwise specifically stated in the claims or descriptions that the steps are to be limited to a specific order, it is in no way intended that any particular order be inferred. In addition, as used herein, the article “a” is intended to include one or more than one component or element, and is not intended to be construed as meaning only one.
It will be apparent to those skilled in the art that various modifications and variations can be made without departing from the spirit or scope of the disclosed embodiments. Since modifications, combinations, sub-combinations and variations of the disclosed embodiments incorporating the spirit and substance of the embodiments may occur to persons skilled in the art, the disclosed embodiments should be construed to include everything within the scope of the appended claims and their equivalents.
Layouni, Khaled, Black, Matthew Lee
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